Electrostatic spray device



Sheet Filed Aug. ll, 1967 mi m mm mm mm T s RM Eu W0. N D mm mm ow B m.N 6 mm mm m 5 mm O? mm Nb H 3 HQ 1 Q T .5 2 mm mm 3 mm S mm N. ow ow 3ow om mm Feb. 4, 1969- Filed Aug, 11, 1967 R. o. PROBST 3,425,625

'INVENTOR' RICHARD O. PROBST United States Patent 3,425,625ELECTROSTATIC SPRAY DEVICE Richard 0. Probst, Indianapolis, Ind.,assignor to Rams- ABSTRACT OF THE DISCLOSURE A remotely controlledelectrostatic spray gun comprising removably interconnected front andrear sections, each comprising a body of insulating material. The frontsection has 1) a liquid passage provided with a valve and terminating ina discharge orifice, (2) a spray charging electrode adjacent theorifice, and (3) a conductive element connected to said electrode andextending rearwardly therefrom. The rear section has a remotelycontrolled motor and a conductive element adapted for connection to asource of high voltage and for contact with the first mentionedconductive element when the two sections are assembled. Means foroperatively interconnecting the motor and valve includes two members anda mechanism for automatically connecting them together when the twosections are assembled and automatically separating them when the twosections are separated.

This invention relates to an electrostatic spray gun for use inspray-coating systems, and more particularly to that type of gun inwhich paint is discharged through a small orifice at high velocity to beatomized by interaction with air and in which the atomized sprayparticles are charged by a needle-like or fine-wire electrode disposedat the side of the orifice. Primarily, the invention is concerned with aspray gun adapted for use in socalled automatic systems, in whicharticles to be coated are conveyed past the gun and in which the gunembodies a paint valve and a valve operating compressedair motor adaptedto be controlled from a remote point. Broadly, such guns are not new.

Among the more important objects of the invention are to produce a gunin which the paint-conveying and spray-charging elements are embodied ina subassembly readily separable from the remainder of the gun forpurposes of replacement; to produce a gun whose outer and larger partsare adapted to be formed from insulating material; and to produce a gunin which the highvoltage supply cable, the paint line or lines, and theconduit supplying air to the valve-controlling motor can all be readilyconnected to the gun in such a manner that, without bending, they willextend away from the forward, or discharge, end of the gun.

A preferred form of gun embodying the invention comprises two removablyinterconnected sections, one an air-motor cylinder adapted to be securedto an appropriate mount and the other a subassembly including a bodyprovided with paint passages, a nozzle, a paint valve, and thespray-charging electrode. The body of the subassembly is formed with aforwardly flaring frustoconical outer surface portion in which islocated at least one opening communicating with the nozzle and adaptedfor connection to a paint conduit. The cylinder is also formed with asimilar frustoconical surface portion containing an opening for thepassage of the high-voltage lead and a second opening communicating withthe airmotor cylinder and adapted for connection to an air line. Meansautomatically severable when the subassembly is removed from thecylinder provide an operative connection between the paint valve and theair motor,

Patented Feb. 4, 1969 and a second and similarly severable meansprovides an electrical connection between the electrode and thehighvoltage lead. The gun may be arranged to be secured to a supportthrough the medium of a two-member clamp which grips the support and inone member of which the cylinder is mounted. Preferably, the paintnozzle and valve are located on the projected axis of such cylinder, thecylinder is adjustable to different positions about such axis relativeto the clamp, and the subassembly is similarly adjustable relative tothe cylinder.

Other objects and features of the invention will appear from thefollowing more detailed description and from the accompanying drawingsin which:

FIG. 1 is an axial section through the gun on the line 11 of FIG. 2;

FIG. 2 is a front elevation of the gun;

:FIG. 3 is a fragmen'tal section on the line 33 of FIG. 2;

FIG. 4 is a fragmental section on the line 4-4 of FIG. 2; and

FIG. 5 is an exploded, isometric view showing, on an enlarged scale, theconstruction of parts at the forward end of the gun.

Referring to FIG. 1, it will be seen that the apparatus there showncomprises a clamp 10, a cylinder 11, and a subassembly 12 containing apaint valve, a paint nozzle, and a spray-charging electrode, all to bedescribed in detail hereinafter. The gun proper consists of the cylinder11 and subassembly 12, the claimp being but one of several forms ofmeans through which the gun may be mounted. The clamp 10 shown comprisestwo members 13 and 14 provided in their opposed faces withsemicylindrical seats for a support to which the gun is to be secured byclamp screws 15 operating between the members 13 and 14. The clampmember 13 embodies a sleeve portion 16 which rotatably receives acylindrical boss '17 on the cylinder 11. A pointed set screw 18 in thesleeve 16, by engaging in a conical recess in the boss 17, secures thecylinder to the clamp member 13. The clamp members v13' and 14, thescrews 15, and the cylinder 11 are all desirably formed of insulatingmaterial.

The cylinder 11 is provided with a rearwardly opening bore 20 slidablyreceiving a piston 21. Bore 20 is sealed by O-rings 91 and 92 slidablyengaging piston 21 and cylinder 11. A cylinder head 22 screw-threadedlymounted in the rear end of the bore 20 is provided with a fonwardlyprojecting central boss 23 which serves both as a stop to limit rearwardmovement of the piston 21 and as a guide for a compression spring 24that urges the piston 21 forwardly in the bore 20.. A lock nut 25engaging the head 22 secures the head in adjusted positron. Axialpassages in the head 22 and lock nut 25 provide for the displacement ofair resulting from movement of the piston 21 in the bore 20.

The intermediate portion of the cylinder 11 lying forwardly of the boss17 is enlarged and provided with a forwardly flaring fru's'toconicalsurface .26. Opening into the surface 26 and communicating with theforward end of the cylinder-bore 20 (FIG. 3) is a screw-threaded recess27 receiving a fitting 28 adapted for connection to an air line 29connected to a source of air under pressure through a conventionalthree-way valve (not shown) operable alternatively to admit compressedair to the bore 20' to force the piston 22 rearwardly against the effortexerted on it by the spring 24, or to vent the bore and permit suchspring to move the piston forwardly.

Projecting forwardly from the intermediate portion of the cylinder 11 isan integral hollow boss 31 from which the subassembly 12 is supported.Such subassembly comprises a body 32 desirably of insulating material,having a rearwardly projecting, externally screw-threaded, an-

nular flange 33 slidable on the boss 31 and receivable in an internallyscrew-threaded collar 34 rotatably secured to the boss 31 by a snap ring35. As will be apparent, the subassembly 12 can be attached to orremoved from the cylinder 11 by rotation of the collar 34 in theappropriate direction.

Screw-threadedly mounted in a boss 37 projecting forwardly from the body32 is a valve cage 38 containing a valve seat 39 with which therecooperates a paint valve 40 connectable, by means hereinafter described,to the piston 21. Valve cage 38 is sealed with the inside surface of:boss 37 ,by an O-ring 93. At its forward end, the valve cage 38 isprovided with a paint-passing opening 42 which is desirably ofnon-circular cross-section to permit the reception of a wrench by whichthe cage can be rotated to effect its insertion into or removal from theboss 37.

A screw-threaded collar 43 mounted on the boss 37 removably secures tothe front end of such boss a nozzlze holder 44 having a bore andcounterbore for the reception of a centrally located nozzle 45 providedwith an orifice 46 (FIG. 2 and FIG. The nozzle is inserted into theholder 44 from the rear thereof through the counterbore, and is providedwith an annular shoulder which seats against the base of thecounterbore, as shown in FIGS. 1 and 5. As is customary in spray guns inwhich paint is atomized by high velocity, the orifice 46 is desirablyelongated to provide a relatively flat, fan-like spray. Also as iscustomary in guns of the type indicated, the nozzle holder 44 shown isprovided with forwardly projecting ears 47 lying on opposite sides ofthe spray.

Extending between the rear face of the nozzle 45 and the front face ofthe valve cage 38 is a seal 49 (see FIG. 5) having an axial paintpassage. Such seal is desirably formed of nylon or a similar plastic andhas a body portion fitting the counterbore in the nozzle holder 44 and alength such that, upon tightening of the collar 43, the seal will becompressed between the nozzle and the valve cage. To facilitate removalof the seal from the nozzle holder it may be provided at its rear endwith an annular flange 50 which overlies one or more diametricallyextending grooves 51 in the rear face of the nozzle holder 44. Thegrooves 51 extend radially outward beyond the periphery of the flange 50to permit the insertion of a tool engageable with the front face of theflange to pry the seal from the holder 44. The rear face of such holdermay be provided with a flange-receiving recess deep enough to insurethat the presence of the flange will not interfere with the clamping ofthe seal in firm engagement with the opposed faces of the nozzle 45 andvalve cage 38.

As will be clear from FIG. 1, the valve 40 is provided with a stem 53which extends rearwardly through a control passage 54 and a seal 55 inthe assembly-body 32 and through and beyond a seal-compressing screw 56mounted in such body. At its rear end, the stem 53 is secured, as byset-screws, in a cylindrical plug 57 which is slidably received in acentral recess in the front end of a piston-stem 58 shown as integralwith the piston 21. When the assembly 12 is secured in position on thecylinder 11, the plug 57 is operatively connected to the pistonstem 58by a means which is automatically releasable upon removal of thesubassembly 12 from the cylinder The means shown for that purposecomprises a pair of balls 60 carried in diametrically opposite holeslocated near the front end of the piston-stem. The balls 60 arereceivable in an annular groove in the plug 57 and, in the mountedposition of the assembly 12, are held in such groove by their engagementwith the inner surface of a sleeve '61 which lines the boss 31,protrudes a slight distance beyond the forward end thereof, and slidablyreceives the front end of the piston-stem. Immediately ahead of theaxial position occupied by the balls 60 when the valve 40 is closed, thesleeves 61 is provided with an internal annular groove 62 deep enough topermit the balls, upon forward movement of the piston and pistonstem, tomove out of the groove in the plug 57 far enough to permit the plug tobe released from the piston-stem. The valve 40, valve-stem 53, screw 56,plug 57, and sleeve 61 are conveniently of metal, but the balls 60 aredesirably of a ceramic.

When the assembly 12 is mounted on the cylinder 11 and the gun is notoperating, the valve 40 is h ld closed by the spring 24, the effort ofwhich is transmitted to the valve through the piston, piston stem, balls60, plug 57, and valve-stem 53. In this condition, the piston 21 isdisplaced rearwardly from the base of the cylinder bore 20. Accordingly,when the collar 34 is unscrewed from the flange 33 and the assembly 12moves forwardly, the spring 24 forces the piston 21 to the base of thebore 20 bringing the balls 60 into the plane of the groove 62 andallowing the balls to move outwardly to free the plug 57 and valve-stem53 for removal from the cylinder 11 with the rest of the assembly 12.The extreme inner ends of the ball-receiving holes in the piston-stem 58have a diameter slightly less than that of the balls to prevent theballs from falling inwardly out of the holes when the plug is removed,while the groove 62 is shallow enough to prevent the balls from movingoutwardly out of the holes. Upon remounting of the assembly 12,insertion of the plug 57 displaces the balls outwardly into the groove62 to permit initial entry of the plug into the recess in thepiston-stem, whereafter tightening of the collar 34 forces the plugrearwardly until the balls enter the plug-groove and are carried out ofthe groove 62 to restore the parts to the condlition shown in FIG. 1.

Paint is supplied to the passage 54 through a fitting 65 mounted in arecess 66 opening at its outer end into a forwardly flaringfrustroconical surface 67 on the body 32 and communicating at its innerend with the passage 54. The fitting 65 is ada ted for connection to apaintsupply line 68. To adapt the gun for use in a system in which paintis continuously circulated, the body 32 may be provided with a secondrecess (not shown) similar to the recess 66 and adapted to receive afitting through which the passage 54 may communicate with a paintreturnline. When no paint-return line is to be employed any additional recessmay be closed by a removable plug.

The spray discharged from the orifice 46 when the gun is in operation iselectrically charged by an electrode 72 (FIG. 5) electrically connectedin a manner described below to a high-voltage lead 73 (FIGS. 2 and 4)extending from the ungrounded terminal of any appropriate highvoltagesource (not shown). Preferably, the electrode is in the form of a finewire extending longitudinally through the nozzle holder 44 andprojecting forwardly just inside one of the ears 47 to a point a slightdistance beyond the front end of such ear.

The connection of the electrode 72 to the high-voltage lead isconveniently effected over a conductive path which includes the metalsleeve 61. Tracing that path forwardly of the gun from the lead 73, andreferring first to FIG. 4, an insulated cable 74 containing the lead 73is secured to the cylinder 11 by a fitting 75 of insulating materialmounted in the forwardly flaring surface 26 of the cylinder. Immediatelyinside the fitting 75, the cable terminates in a conductive button 76connected to the lead 73 and engaged by one end of a conductivecompression spring 77 the opposite end of which engages the head of ametal pin 78 slidably received in the cylinder-body 11 and disposed inan oblique position coaxial with the fitting 75 with its inner end heldin contact with the sleeve 61 as a result of the force exerted on it bythe spring 77. When the subassembly 12 is secured in place by the collar34, the front end of the sleeve 61 is held in contact with a metal ring80 mounted in an annular recess in the body 32 at the base of the flange33. A spring wire 81 soldered to the ring 80 extends forwardly throughthe body 32 and emerges at 82 (FIG. 5 from the front of the boss 37 tomake contact with the rear face of the nozzle-holder 44.

Preferably, the Wire 81 is bent at 82 to provide a first, or contact,portion 83 extending generally chordally of the end face of the boss 37and at an acute angle thereto, and a second, or guiding, portion 84which extends rearwardly to be loosely received in a recess 85 in theboss 37. The recess 85 is deep enough to allow the contact portion 83 tobe resiliently bent to the extent necessary to permit the seal 49 to beclamped between the valve cage 38 and the nozzle 45 when the collar 43is tightened.

To provide electrical connection between the contact portion 83 of wire81 and the electrode 72, and thus to complete the conductive path fromthe high-voltage lead 73 to the electrode, the rear face of the nozzleholder 44, the surfaces of the grooves 51, and the rear end of theelectrode 72, which extends into one of the grooves 51, are all coatedwith a continuous coating of conductive paint such, for example, as thatdisclosed in US. Patent 3,021,- 077 to W. D. Gauthier. Thus, althoughthe nozzle holder 44 is of insulating material the electrode 72 will beconnected through the conductive paint coating to the wire 81irrespective of the orientation of the nozzle holder with respect to theaxis of the gun.

Returning to the engagement of the sleeve 61 with the ring 80, it isnoted that if the contact between those two elements werecircumferentially continuous any paint escaping rearwardly past the seal55 and screw 56 would be trapped within the sleeve, where its presencewould be undesirable. Accordingly, the front end of sleeve 61 isprovided with notches through which any paint entering the sleeve canflow by gravity into the interior of flange 33 to escape therefromthrough an opening 88 extending radially through the flange. Theappearance of paint at the opening 88 constitutes a warning that theseal 55 is leaking.

Reference has been made to the scarew 18 which, by engaging in a recessin the boss 17, secures the cylinder 11 to the clamp member 13.Desirably, the boss 17 has a plurality of screw-receiving recesses 88spaced angularly about the axis of the boss, thus providing a pluralityof angularly spaced positions for the cylinder 11, relative to the clampmember 13 or other gun support,

Just as a plurality of positions are provided for the cylinder 11relative to the clamp, it is desirable that a plurality of positions beprovidetd for the subassembly 12 relative to the cylinder. For thispurpose, the boss 31 of the cylinder may be provided with a key 90receivable in a key-way in the inner surface of the flange 33. It hasbeen found convenient to provide the flange 33 with two of such key-Waysspaced 90 apart.

When assembled as shown in FIGS. 1-4 and applied to a suitableclamp-engaged support, the gun is readied for operation by connecting toit the paint line 68, the high-voltage lead 73, and the air line 29. Inthe condition shown, the paint valve 40 is closed by the spring 24 andthe pressure of the paint behind it, To operate the gun, air is admittedto the cylinder-bore 20 from the air line 29, thus forcing the piston 22rearwardly and cansing the valve 40 to open. Upon opening of the valve40, paint supplied under high pressure to the gun through the paint line68 will be discharged through the orifice 46 and atomized into a spraythe particles in which will be charged by ions emanating from theelectrode 72. To terminate spraying, the cylinder 20 is vented to permitthe spring 24 to move the piston 22 forwardly and close the valve 40.

The rotatability of the cylinder 11 relative to the clamp member 13 andof the subassembly 12 relative to the cylinder provides a number ofdifferent arrangements of the directions in which the air line 29, thepaint line 68, and the high-voltage lead 73 can extend from the gun.Because of the possibility of disposing the subassembly 12 in any of aplurality of different positions about the axis of the gun, there shouldbe a corresponding number of paint-escape openings 88 in the flange 33so that one of said openings will always be at the lowest point of theflange when the gun axis is horizontal, as it will most frequently be incommercial installations.

If at any time any part of the front section consisting of thesubassembly 12 requires repair that section can readily be removed fromthe rear, or motor, section by merely unscrewing the collar 34 from theflange 33. As explained above, the unscrewing of the collar brings theballs 60 into the plane of the groove 62 and thereby allows the plug 57to be released from the piston-stem 58 and the entire subassembly to beremoved, leaving the rear section of the gun and its connections to theair line 29 and lead 73 undisturbed. If necessary or desirable theremoved subassembly can be disconnected from the paint line 68 andreplaced with another. The ready severability of the gun sections isalso advantageous in the case of a gun used to spray paint of differentcolors. In such a case, there could be, for each color of paint to besprayed, a separate subassembly connected through a paint line 68 to itsown source of paint under pressure, Since the valve 40 of eachsubassembly used closes with pressure, it is not necessary to relievethe associated paint line 68 of pressure while the subassembly isremoved from the motor section, as the pressure in the passage 54 willmaintain the valve closed.

Ready severability of the two gun sections, in addition to facilitatingrepair or replacement of the front section, also facilitates repair orreplacement of the rear, or motor, section. It can be removed from thefront section and the clamp 10 without disturbing either the connectionof the paint line 68 or the mounting of the clamp on its support.

I claim:

1. A remotely controlled electrostatic spray gun comprising front andrear sections each having a body formed of insulating material;releasable means for rigidly interconnecting said bodies; said frontsection having a liquid passage containing a valve and terminating in adicharge orifice for forming liquid supplied to said passage into aspray; a conductive means in and extending longitudinally of the frontsection body and having a front end portion forming a spray-chargingelectrode; said rear section comprising a motor having a reciprocablepoweroperated element; a conductive means carried by the rear sectionbody, adapted for connection to a high-voltage source, and having aportion disposed to engage the rear end of the first-mentionedconductive means where the two bodies are connected together by saidinterconnecting means; and means for operatively interconnecting saidreciprocable element with said valve, said last mentioned meansincluding first and second members respectively movable with said valveand power-operated element and a device automatically operable uponinterconnection of said bodies to connect said members together and uponseparation of said bodies to disconnect said members.

2. A spray gun according to claim 1 wherein said liquid passage has, ina laterally presented surface of the first-section body, an inletopening adapted for connection to a paint-source, said front and rearsections being relatively angularly adjustable about the axis of saiddischarge orifice.

3. A spray gun according to claim 1 wherein the rear-section body hasmeans for securing to it a high voltage lead extending laterally outwardfrom the body, and a support for said rear-section body, saidrear-section body being angularly adjustable relative to said supportabout the axis of said discharge orifice.

4. A spray gun according to claim 1 wherein the bodies of said front andrear sections are circular in cross-section.

5. A remotely controlled electrostatic spray gun comprising front andrear sections each having a body; releasable means for rigidlyinterconnecting said bodies; said front section having a liquid passagecontaining a valve and terminating in a discharge orifice for formingliquid supplied to said passage into a spray; said rear sectioncomprising a motor having a reciprocable poweroperated element; andmeans for operatively interconnecting said reciprocable element withsaid valve, said last mentioned means including first and second membersrespectively movable with said valve and poweroperated element and adevice automatically operable upon interconnection of said bodies toconnect said members together and upon separation of said bodies todisconnect said members.

6. A spray gun according to claim wherein said first member is slidablyreceivable in a recess in said second member, said connecting devicecomprising a connecting element carried by said second member andengageable with said first member to interconnect the members for jointvalve-operating movement, said connecting element being movable out ofengagement with the first member, and means in the rear-section body forholding said element in engagement with the first member only when thetwo bodies are interconnected.

7. A spray gun according to claim 5 wherein the frontsection body has aforwardly flaring frustoconical surface, the paint passage having insaid surface an inlet opening adapted for connection to a paint source.

8. A spray gun according to claim 5 wherein said motor is an air motorhaving a cylinder bore and a piston slidable therein, said rear-sectionbody having a forwardly flaring frustoconical surface and an air passageextending from an inlet opening in said surface to said cylinder bore.

9. A spray gun, comprising front and rear sections each having a body,said front section having a liquid passage terminating in a dischargeorifice at the forward end of the front section, a valve in said passagemovable forwardly of the gun into closed position, said front sectionbeing separable from said rear sections by forward movement from anoperating position, releasable means for retaining said first section inoperating position on said rear section, a reciprocable valve operatingmember mounted in said rear section and movable rearwardly from aforwardmost position, means biasing said member toward such forwardrnostposition, power-operated means for moving said member rearwardly, areleasable operative connection between said member and valve for movingthe valve rearwardly from closed position when said member is movedrearwardly upon actuation of said power operated means, said connectionbeing so constructed and arranged that with the front section inoperative position on the rear section and with the valve closed saidmember will be displaced rearwardly from its forwardmost position, andconnection controlling means for automatically releasing said connectionwhen said member moves into its forwardmost position under the influenceof said biasing means upon forward movement of the front section fromits operative position on the rear section and for reestablishing saidconnection when the front section is moved rearwardly into suchoperative position.

10. In a spray gun, a front section having a discharge orifice and valvemeans for controlling flow of liquid to said orifice, a rear sectioncomprising a valve-operating member movable in opposite directions froman intermediate position, releasable means for securing said twosections together in fixed relationship, a releasable operativeconnection between said valve and said member so constructed andarranged that with said two sections secured together in said fixedrelationship said valve will be closed and said member will be in itsintermediate position, power-operated means for moving said member invalve-opening direction from its intermediate position, means biasingsaid member for movement in valveclosing direction to and beyond saidintermediate position, and connection-releasing means being operative torelease said connection when said member is moved from its intermediateposition by said biasing means.

11. An electrostatic spray gun comprising front and rear sections eachhaving a body; releasable means for rigidly interconnecting said body;said front section having a liquid passage containing a valve andterminating in a discharge orifice for forming liquid supplied to saidpassage into a spray; conductive means carried by the first section andincluding a spray charging electrode; said rear section comprising amovable control member; and releasable means for operativelyinterconnecting said movable control member with said valve; andconductive means in the second section adapted to be connected to a highvoltage source, said two conductive means respectively having severablecooperating portions held in conductive engagement with each other bysaid interconnecting means.

12. A spray gun according to claim 11 wherein said first and secondsections are angularly adjustable with respect to each other about anaxis, one of the severable cooperating portions being so formed tocontact the other in different angular position of the two sections.

References Cited UNITED STATES PATENTS 3,248,059 4/1966 Fischer et a1.239-15 EVERETT W. KIRBY, Primary Examiner.

U.S. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,425,625 February 4, 1969 Richard O. Probst It is certified that errorappears in the above identified patent and that said Letters Patent arehereby corrected as shown below:

In the heading to the printed specification, lines 3 and 4 "Ramsburg"Column 3, line 63 "cylinder should read should read Ransburg should readscrew cylinder. Column 5 line 35, scarew" Column 8, line 25 "body"should read bodies Signed and sealed this 31st day of March 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

